Numerous applications exist for fluid, and specifically liquid, supply systems wherein the fluid is distributed through a manifold having a plurality of outlet stations. Illustrative of such an application is a system of the type utilized in meat slaughter and packing houses. At various stages during meat processing, cleaning guns, to which a liquid is supplied, are provided. The system provides automatically controlled high-pressure hot water or other fluids for distribution throughout the plant through fixed headers to actual use points. The guns, or wands, can be used for general spray-down, cleaning and rinsing.
Because of the plurality of stations which are provided, the demand created by the overall manifold system can vary significantly. Typically, a plurality of pumps are provided to pump the cleaning liquid from the reservoir in which it is stored to the various stations. With some prior structures, pumps having a sufficient aggregate capacity to provide the maximum demand of liquid are provided and are kept on line at all times during operation of the plant. With these structures, there is always some measure of waste in energy expended in moving fluid through a supply line to the manifold. When the demand created by the various stations is high, the actual waste of energy expended will be relatively low. The consumption of fuel in running all of the pumps will be at a maximum, but, because of the high demand, the expenditure of fuel in running the pumps can be justified.
On the other hand, however, when the demand is relatively low, a greater number of pumps than necessary to satisfy the demand will be running. Under such circumstances, the additional energy expended in running the unnecessary pumps is wasted.
Various systems have been devised to automatically bring on-line and cut off-line additional pumps, as necessary, in response to the actual demand created by the manifold stations. Such systems have, heretofore, however, been responsive to pressures or pressure drops sensed within the system. Illustrative of such a system is that disclosed in U.S. Pat. No. 3,639,081 issued to John Gray and Gene W. Anderson on Feb. 1, 1972. All other systems of which applicant is aware function in response to sensing of pressures and pressure increases and drops.
Such systems, however, have some inherent deficiencies. The accuracy of such systems is completely dependent upon the correct sensing by, and the calibration of, the various sensing instruments. Additionally, changes in the number of pumps on line are not particularly responsive to the actual demand since there is a time lag between the reduced demand and the sensing of a reduced pressure in the system.
It is to these deficiencies in prior art systems that the invention of the present application is directed. The present invention provides means for increasing and decreasing the number of pumps on line without the shortcomings inherent in these prior art systems.